Optical glass



Patented June 17, 1930- UNITED STATES PATENT OFFICE MURRAY R. SCOTT, Oli ROCHESTER, YORK, ASSIGR'OR TO BAUSOE & LOHB OPTICAL 00., O1 ROCHESTER, NEW YORK, A CORPORATION OI NEW YORK OPTICAL GLASS V I Drawing.

My invention relates to an improvement in the composition of optical glasses known generally as dense barium crown lass. The refractive index of this type of g ass ener-- ally varies'from 1.56 to 1.63 and the lspersion, as expressed by v (Greek letter nu), generally varies from 40 to 64. 7 It is well known that dense barium crown glass will tarnish on the surface when ex 10 posed to severe atmospheric conditions.

This tarnish usually appears as spots or discolorations on the surface of the glass and in Bad cases it causes an-iridescent efi'ecton the surface. Thistype of glass is used in 5 a variety of optical products, such as for example, in fie d glasses, photogra hic ob- I jectives,'and fused bifocal lenses. his surface tarnishin therefore, presents a ver serious and o jectionable defect since 1t greatly impairs the optical performance of the instrument or device in which lenses made of this type of glass are used.

One of the objects of the present invention is to provide an improved optical glass;

another object is to provide a dense barium crown glass that will be resistant to tarnishing.

I have discovered that by using zirconium in'a barium crown glass batch the resistance to tarnishing, under atmospheric exposure,

will be greatly increased. This is accorn plished by substituting not over 5% of zirconium oxide for an equivalentpart of the vzinc oxide or other materials that are found scribed.

An example provide I Boric oxide in abat ch for aglass of the character de ti a glass batch which will" a dense barium crown glass, which Applicatlomfled June 11, 1928. Serial-Ho. 284,653.

' Per cent Arsenic oxide 7 3 'Antimony oxide 1. 03 Zirconium oxide 3. 00

" cases when the zirconium oxide is substituted for the zinc oxide, there is'a tendency to raise the refractive index of the resulting glass.

. I claim as m invention;

1. A dense arium crown optical glass which is resistant to tarnishing comprising over 25 percent of barium and under.5 percent of a zirconium compound.

2. A barium glass suitable for optical purposes having a refractive index between 1.56 and-1.63 and a dispersion as expressed by '1' between 40 and. 64 and compnsin inv its composition a suflicient amount 0 a zir- -conium compound to rendertheglass re"- sistant to tarnishing.

3. A dense barium crown optical glass comprising a suflieient amount of a zirconium compound to render the glass re-' sistant to tarnishing.

' MURRAY R. SCOTT. 

